[PATCH 1/5] Rewrite final cleanups

[Tom Tromey]

Lancelot> My train of thought was
Lancelot> 1) This `system ("rm -rf ...")` could be replaced with
Lancelot> std::filesystem::remove_all
Lancelot> 2) At least one overload of remove_all can throw
Lancelot> 3) What would happen if a cleanup throws (either an existing one, or one
Lancelot> to change/introduce in the future).

Makes sense.

I filed a bug for this:

https://sourceware.org/bugzilla/show_bug.cgi?id=31420

... and also a C++17 meta-bug, and various C++17 to-do items I've
thought of in the past.

Lancelot> FWIW, I skimmed through the rest of the series, and looks reasonable to
Lancelot> me.

Thanks.  Normally I would not rush this, but the current state of the
tree is preventing us from doing a merge here at AdaCore, as DAP exiting
is currently broken.

So, I am going to check this in.

Tom